1. Field of the Invention
The present invention relates to heat transfer means and, more particularly, to a three-phase heat transfer structure, which uses phase change material to store excessive amount of heat energy, enabling heat to be smoothly dissipated when the environmental temperature lowered.
2. Description of the Related Art
Following fast development of computer industry, a variety of high-precision electronic devices have been continuously created. These high-precision electronic devices achieve high operation speed, however they release high heat during operation. In order to keep high-precision electronic devices functioning normally, the surrounding temperature must be maintained within the acceptable working range. Various cooling arrangements have been disclosed employing thermal tube technology. A thermal tube has a wick structure on the inside for quick transfer of a working fluid to carry heat from a heat source, for example, a CPU or power transistor to a heat sink.
FIG. 1 illustrates a cooling structure 1a according to the prior art. The cooling structure 1a comprises a heat conducting plate 10a extruded from metal (for example, aluminum), a heat sink 11a extruded from metal (for example, aluminum) and mounted on the top sidewall of the heat conducting plate 10a near one end, and a plurality of thermal tubes 13a provided on the bottom side of the heat conducting plate 10a. The heat sink 11a comprises a plurality of upright radiation fins 12a arranged in parallel. The thermal tubes 13a are made of copper, having a wick structure and a working fluid on the inside. When in use, the thermal tubes 13a are connected to the heat source (CPU or power transistor) to absorb heat from the heat source, enabling heat to be further dissipated into the air through the radiation fins 12a of the heat sink 11a. This design of cooling structure 1a is still not satisfactory in function. Because an advanced CPU produces high heat during its operation, the heat dissipation speed of the solid heat sink 11a and the solid heat conducting plate 10a is lower than the heat producing speed of an advanced CPU. Therefore, the aforesaid conventional cooling structure 1a cannot satisfy the need.
The present invention has been accomplished under the circumstances in view. It is therefore the main object of the present invention to provide a three-phase heat transfer structure, which uses a phase change material to store heat energy and to change the phase from solid state to liquid state when absorbed a certain amount of heat energy, enabling absorbed heat energy to be smoothly dissipated into the air when the surrounding temperature lowered. It is another object of the present invention to provide a three-phase heat transfer structure, which prevents breakdown of the computer system due to excessive high temperature. To achieve these and other objects of the present invention, the three-phase heat transfer structure comprises a heat conducting plate disposed in contact with a heat source for absorbing heat energy from the heat source, a heat sink mounted on the heat conducting plate near one end, and at least one thermal tube embedded in the heat conducting plate and extended through two distal ends of the heat conducting plate, each thermal tube having a wick structure and a working liquid on the inside. The heat conducting plate comprises at least one recessed receiving space in the top side near one end remote from the heat sink, and a phase change material filled in the at least one recessed receiving space. The phase change material changes the phase from solid state to liquid state when storing heat energy absorbed through the heat conducting plate. When the environmental temperature lowered, the phase change material is returned to solid state.